1. Field of the Invention
The invention relates to a hydraulic drop forging press of above-floor construction, comprising a prestressed press frame consisting of a lower crosshead and upper crosshead with columns which connect these together and which are prestressed against compression supports disposed between the inner sides of the crossheads.
2. Description of the Prior Art
Hydraulic forging presses of above-floor and below-floor construction based on the principle of combined plunger and column guiding are known. In these, the press plunger, which slides in a cylinder in the upper cylinder crosshead, is guided therein by means of a liner. In addition, a moving crosshead which is rigidly fixed to the plunger is guided on the columns which connect together the cylinder crosshead and lower crosshead. By virtue of this rigid connection between the plunger and the moving crosshead, the total moment exerted by the pressing force can be transmitted to the plunger, and must in such a case be absorbed by the liner in the cylinder. This causes heavy wear of the guide liner and can lead to scoring of the plunger and to leaking of the packing.
This and other methods of guiding the moving crosshead and plunger in forging presses are known from the literature (see Ernst Muller, "Hydraulic Presses and Hydraulic Pressure Systems", volume 1: "Forging Presses", 3rd edition 1962, Springer-Verlag, pages 32 to 34 and 58 to 65, but in particular page 62). This states that in the case of single cylinder presses with the plunger fixed into the moving crosshead, a column guide system can no longer be used alone, because the plunger opposes any inclination of the crosshead, and in the case of eccentric forging, contact pressure is also transmitted to the cylinder liner. As stated heretofore, this leads to increased wear, the result of which is often gland leakage.
The drawback of all these types of construction is that cylinder liners which are used as guide elements are subjected to heavy wear, and the dust resulting from the abrasion is picked up by the operating medium. If this state is improved by using an articulated support for the piston or plunger, the latter is no longer used for guide purposes. The liner is then no longer subjected to wear as in the case of a rigid connection between the plunger and moving crosshead. Because of the fact that in this case only the moving crosshead is guided on the columns, a constant guide distance is now obtained, which is defined by the guide length or overall height of the moving crosshead.